Building a Cooler Mash Tun

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building a cooler mash tun

 This article will break down the six basic steps to building your own cooler mash tun.  Everything can be purchased at your local hardware store.

1. Purchase the Equipment
2. Remove the Stainless Steel Braiding
3. Connect the Fittings to the Braiding
4. Connect the Valve and Hose
5. Assembling the Mash Tun
6. Cleaning After Use

All-grain brewing requires the use of a mash tun.  The mash tun is used to steep the various grains selected for brewing beer.  The grains are mixed with water and sit for about an hour, then the mixture is filtered and drained off to the boil pot.  More water is added to rinse the residual sugars from the grains.  To find out more on these specific sugars check out our brewing sugars article.  In the home brew setting you can either have a cooler or pot as a mash tun.  The cheaper option by far is the cooler version which will total somewhere around $70.  Check out our gravity fed all grain brew tower that uses this cooler mash tun.  As a comparison the pot version could cost anywhere from $180 -$400.  The cooler version usually uses a braided stainless steel hose as its filter, where a pot version would use a custom false bottom.  I have tried using a 5 gallon round cooler with a false bottom but I did not get the results that I wanted out of it.  I then moved on to build this and so far it has been working great for me.

Purchase Equipment (30 minutes)

1. 52 qrt well insulated Cooler (Coleman Xtreme is what I used.)

Brass Option (Cheaper)
2. 4 ft of Plastic Hose (Food Grade Quality)
3. 1/2″ MIP to 1/2″ barb (brass) (Watts A-385)
4. 1/2″ Ball Valve (brass)
5. 2 Food Grade Rubber O-Ring (No. 15, 1/8 thick)
6. 1 1/2″ Pipe Nipple (MIP) (brass) (Watts A-836)
– or –
Complete Stainless Steel Cooler Kit

7. 1/2″ FIP to 1/2″ Barb (brass) (Watts A-390)
8.  2-4ft of SS Washing Machine Connector (Eastman 98503)
9. 1/2″ Barb to 1/2″ MIP (brass) (Watts A-385)
10. 1/2″ FIP Pipe Cap (Watts A-819)
11. 3 1/4″ to 5/8″ SS Hose Clamps
12. Pipe Thread Tape (white)

Gather all of the equipment mentioned in the list above.  These parts are the easiest to come by and work with.  Everything above can be purchased at your local hardware store, I have included the specific part numbers for exact matches in Lowes/Home Depot.  I have also included a kit that is offered by Midwest Brewing Supplies, its has stainless steel components. As far as the cooler goes, I think the best deal going right now is at K-mart, I picked up this 52 quart well insulated Coleman cooler for about $35.

Remove the Stainless Steel Braiding (15 minutes)

In this step you will be removing the end connectors of the SS braiding that you purchased and removing the internal hose.  You will saw off the end connectors with a fine blade hacksaw.  To do this first tape up the edges near the connectors, this prevents the braiding from coming unraveled.  Then take a fine bladed hacksaw and saw through the stainless steel braiding and the rubber hose completely.  Repeat for the other side of the hose. 

removing original fittings on SS braiding

removing original fittings on SS braiding

Next remove the internal rubber hose from the braiding.  This is easily accomplished with the help of someone else, its a constant pull and push activity.  Remember not to pull too hard, you may break the braiding. It works like a Chinese finger trap you will need to inch it slowly by pushing it then pulling it.

removing rubber hose inside SS braiding

removing rubber hose inside SS braiding

Connect the Fittings to the Braiding (5 minutes)

In this step you will be connecting the new fittings on the SS braiding.  Gather the new SS braiding along with parts 7,9,10 and two hose clamps. 

equipment for connecting fittings to braiding

equipment for connecting fittings to braiding

You will need to attach the barbs on each end of the SS braiding.  To do this you will need to slide the hose clamp onto the braiding then push the barb into place.  Next slide the hose clamp into position and tighten.  Do the same for each end.

both ends attached to SS hose

both ends attached to SS hose

Connect the Valve and Hose (5 minutes)

In this step you will be assembling the ball valve to the plastic hose.  Gather part numbers 2,3,4,5 and one hose clamp. Screw together the 1/2″ MIP to 1/2″ barb to the ball valve and remember to use the pipe thread tape. Next you will need to slide the hose clamp down the plastic hose then push the barb into place.  Then slide the hose clamp into position and tighten. The picture below should be able to help you out.

ball valve and hose connection

ball valve and hose connection

Assembling the Mash Tun (5 minutes)

The next step will be assembling the mash tun.  Before this can be performed you will need to remove the existing valve on the cooler or create a 1/2″ hole for the new fixtures to fit into.  If using the coleman extreme cooler as picture below make sure to just remove the plastic spigot and not the plastic that surrounds it.  To assemble the mash tun push the 1.5 inch pipe nipple though the hole in the cooler and place O-rings on each side of the cooler. 

pipe nipple pushed through cooler with O-ring

pipe nipple pushed through cooler with O-ring

Next screw on the connector attached to the SS braiding, then from the other side screw on the ball valve/hose portion.   Watch out for over tightening of the screws as it may prevent the O-ring from functioning correctly which can led to leakage.

SS braiding with fitting connected to pipe nipple

SS braiding with fitting connected to pipe nipple

I would recommend testing the mash tun by filling it with water and draining it a few times before actual use, if it appears to be leaking make sure your O-rings are not over compressed.  If it still seems to leak, look into purchasing some rubber washers, if the leak is a drop a minute then its nothing to worry about.

everything hooked up in a big cooler

everything hooked up in a big cooler

everything hooked up in a round cooler

everything hooked up in a round cooler

Cleaning After Use (10 minutes)

Make sure to clean the mash tun after each use, almost immediately afterwards is easiest.  Clean the mash tun with a small amount of mild soap and rinse thoroughly with water.  Disconnect the internal braiding and clean it from any grains that may be stuck in it.  Also wash off the ball valve and rubber hose, remember to hang this in a dry place for at least a day to dry(be careful of leaving in mold prone places).  That should do it, remember the next time you want to use the mash tun just rinse it out really good with warm water.

If anyone has any questions about the process described above, write a comment below and I will respond to it.  Enjoy and go brew more beer!


Comments

20 Responses to “Building a Cooler Mash Tun”
  1. john_brewer says:

    I was planning on buying a round 5 gallon cooler and using a false bottom, why does the example above use such a huge cooler?

  2. Roko Peros says:

    John,

    I have experimented with both the 5 gallon round and 12 gallon rectangle coolers. As I mentioned above I didn’t get good results by using a 5 gallon round cooler with false bottom. I think this was mostly due to the fact that I was brewing beer with at least 9-12 pounds of grain. Calculating it out with a grist-to-water ratio of 2 quarts per pound you would have to around 4-5 gallons of water plus the grains for the mash(didn’t seem to fit). I use the 12 gallon rectangle cooler because I will be transferring over to a 10 gallon system around the end of summer and it should even be sufficient then. Thanks for the comment and let me know if you have any other questions.

  3. adam says:

    Why does this design require two barbs on the SS braid? Does the other end hook up to anything? I’ve seen other designs where one end was crimped. Thanks and great DIY.

  4. Roko Peros says:

    To be honest, when building the mash tun, I didn’t even think of crimping the other end. I was more concerned with keeping the hose on the bottom of the tun. Adding the barb gives a bunch of weight to the hose which is otherwise light as a feather. With the barb the hose tends to lay on the bottom of the mash tun and gets the job done. Crimping is cheaper, so I would definitely recommend it for the budget conscience. Thanks for the comment!

  5. Marshall says:

    First off, thanks for the instructions!! I’ve followed every step exactly (even down to the type of cooler) and I’m running into a problem: when I insert the nipple into the cooler’s drain hole (spigot removed, white plastic thing remains), add the o-rings, and screw both ends on, there are spaces on both the inside and outside… leaving the whole thing quite loose. I was thinking about adding SS washers to the inside and some fender washers to the outside. How did you get yours so snug???

    Thanks!

  6. Roko Peros says:

    Sounds like a pretty good solution to me. Not sure why yours is not snug on both ends, did you use a 1.5 inch pipe nipple or is it longer?

  7. Jim L says:

    Is it safe to say that the smaller, round cooler is better for “partial mash” brewing, in which some extract is used to offset the need for a huge mash tun, and the large rectangular cooler is better for all grain?

  8. Roko Peros says:

    Yeah I would definitely agree with that Jim.

  9. Mark Robinson says:

    I just finished making a cooler mash tun using your materials/directions and it turned out great. I did have to add a washer on the outside between the cooler and the O-ring to make the ball valve assembly more snug. I used a Coleman 48 quart rectangular cooler that I purchased at Dick’s Sporting Goods for $25. All the other materials wer $50 at Home Depot. It’s sitting by the sink half full of water and no leaks yet!!! Thanks for sharing the design.

  10. Tony says:

    I’m just getting into all-grain and wanted to save money. I made you’r design for a coleman round water cooler 5 gal. I tried a 1.5 nipple and found it too long so I used a shorter one about 1 in. This worked pretty good, but I could’nt shut the valve all the way. so I worked on the handle so it would let me shut the valve off (I just twisted it.) Thanks for the help. It saved me a lot of trouble .

  11. NikonTom says:

    I made mine watertight with silicone. I couldn’t handle the infrequent drips.

  12. Hey Roko, great write up. If you worry about the O-rings leaking, you can use drinking water safe epoxy to mold all around to create your own seal. I always had issues with mine leaking after a few batches after the strike water hit it and rapidly changed the temperature. The epoxy molds right to the surface and creates a great seal. Full details can be found over at my blog post:
    http://lifefermented.wordpress.com/2013/05/20/diy-mash-tun/

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